Firing mechanism for a depth charge



Feb; 12, 1957 R. o. BEACH FIRING MECHANISM FOR A DEPTH CHARGE Filed Aug.18, 1945 4 Sheets-Sheet l HgK-Up AMPLIFIER 2365? 46 97;; 44 T f Ll 58 E96| e2 e3 64 Wm amm Ra Beaeh Feb. 12, 1957 R. o. BEACH 2,780,992

FIRING MECHANISM FOR A DEPTH CHARGE Filed Aug. 18, 1945 4 Sheets-Sheet 273 l i 72 7'4 4s 75 84 H 76 4| "5 I J: :3 n l 1111 I e sq SI 1 67 5 2261 66 49 I i :l 9|

53 f E V 1 34 {HT 54 W V I 46 I V 37 B as 55 l ll I 0 I. 0 22 g V 6( 5 LL- 1957 R. o. BEACH I 2,780,992

FIRING MECHANISM FOR A DEPTH CHARGE Filed Aug. 18, 1945 I 4 Sheets-Sheets Feb, 12, 1957 w R. o. BEACH 2,730,992

7* FIRING MECHANISM FOR A DEPTH CHARGE Filed Aug. 18, 1945 4Sheets-Sheet 4 37 R 0. flea/0h um/mm United States Patent FIRING,MECHANISM FOR A DEPTH CHARGE Ronald 0. Beach, Washington, D. C.

Application August 18, 1945, Serial No. 611,432

9 Claims. (Cl. 102-97) (Granted under Title 35, U. S. Code (1952'), sec.266) This invention relates generally to a firing mechanism for a depthcharge. More specifically, the invention relates to a hydrostaticallycontrolled switch adapted to close a firing circuit of the depth chargeat a predetermined depth of submergence thereof.

b An object of the present invention is to provide a new and improveddepth charge firing mechanism in which a hydrostatically controlledswitch operates at a preselected one of a plurality of depths to closethe depth charge firing circuit.

Another object is the provision of a hydrostatically controlled switchfor a depth charge firing mechanism which will not be prematurelyoperated by pressure waves such, for example, as pressure wavesresulting from the detonation of an explosive charge within the vicinityof the depth charge.

Still another object is to provide a switch of the aforedescribedcharacter which operates satisfactorily over a wide range of depthssuch, for example, as 50 to 1500 feet. i

A further object is the provision of a new and im proved hydrostaticallycontrolled switch for a depth charge firing system which will render thesystem ineffective when the depth charge has descended to apredetermined depth in. the. event the depth charge is not fired duringthe descent thereof.

A still further object is the provision of a hydro.- staticallycontrolled switch which is rugged in construction and economical tomanufacture.

Additional objects and advantages are those contained. in and pertainingto the novel construction and arrangement of the elements of the deviceof the present invention, as will more clearly appear in the followingdescription taken in connection with the accompanying drawings of which:

Fig. 1 is a top plan view of a depth charge pistol employing the deviceof the present invention;

Fig. 2 is a sectional view, with certain parts in elevation, takensubstantially along the line 2 -2 of Fig. 1;

Fig. 3 is a view. similar to that of Fig. 1 with the top cover plateremoved;

Fig. 4 is a vertical sectional view of the device of the presentinvention according to the preferred embodiment thereof;

Fig. 5 is a view in section taken along the line 5-5 of Fig. 4;

Fig. 6 is a view in section takenv along the line 6-6 of Fig. 4;

Fig. 7 is an enlarged detailed view of the stepped contact member;

Fig. 8 is an enlarged detailed, view taken along the line 88 of Fig. 4;and,

Fig. 9 illustrates in diagrammatic form a complete depth charge firingsystem including the hydrostatic switch of the present invention.

Referring now to the drawings wherein like characters of reference referto like parts throughout the several views and more particularly toFigsA through 8 inclusive, the numeral 10 dssignates a cylindrisalmember having 'ice an axially disposed bore adapted to receive a tubularmem-. ber 11. The aforesaid axially disposed bore extends through thecylindrical member 10, the uppermost portion of the bore having areduced diameter such that the tubular member 11 engages the shoulder 12in an abutting relation therewith.

A rod 13 composed of any suitable electrical conducting material such,for example, as brass is arranged to. pass slideably through theaforesaid bore and tubular member 11. The cylindrical member 10 isprovided with a circular flanged portion 14 within which is disposed adisk 15 preferably formed of Lucite, the rod 13 extend. ing through ahole in the disk. Arranged within a recessed portion of the disk 15 is aresilient contact element 16, one end of the contact element beingsoldered to the upper extremity of rod 13 and the other end there-. ofbeing brought out through an ear-like portion 17-- of the disk adaptedto fit into a cut-away portion of the flange 14. The recessed portion ofthe disk also contains a quantity of a suitable insulating grease packedabout the contact element 16 therein whereby the area of the protrudingportion of the element only is exposed, there,- by effectively reducingthe electrical leakage due toelectro: lytic action which otherwise wouldexist between the contact element and its coacting step member,hereinafter described. A rubber gasket 18 is provided between the disk15 and the cylindrical member 10 in order to insure a water-tightconnection therebetween. A metallic disk 19 is placed over the disk 15with suitable insulating means 21 being arranged therebetween, and theassembly including disk 15, contact 16, gasket 18, disk 19 andinsulating means 21 is; secured to the flanged portion 14 of thecylindrical member as by crimping the flanged portion to the disk 19;.In order to electrically insulate rod 13 from member 10 and the tubularmember 11, a suitable piece of tubing 22 such, for ex.- ample, as Sarantubing is disposed about the rod, the upper end of tubing 22 beingprovided with a circular lip 23 such that rod 13 will be sealed by thecold flow of gasket 13 when the aforesaid assembly is crimpedto theflange 14 and immersed in a body of water.

A metallic bellows 24 is. disposed about the cylindrical member 1% andthe tubular member 11, the upper end of the bellows being centered by ashoulder 25 formed integrally on the member 10 and thereafter beingsoldered to the flange 14.

A substantially cylindrical casting 26 is provided having an axial borefor receiving the bellows 24, a shoulder 27 being provided therein forcentering the lower end of the bellows which is soldered to the interiorof the casting at 28. A bore of lesser diameter extends through thecasting 26 through which passes rod 13 and tubing 22. The tubular member11 is provided with a reduced end portion 29 for receiving a washer 31adapted to sup.- port and center a stainless steel compression spring32, a second washer 33 being provided to further center spring 32. Thelower extremity of the cylindrical casting 26 is externally threaded toreceive a stainless steel extension spring 34 having a greater number ofturns and a greater degree of stifiness than the compression spring 32.

A set of three threaded telescopic adjusting members is provided in thedevice of the present invention and comprises an adjusting member 35disposed about the tubular member 11 and arranged within the compressionspring 32 for varying the depth at which the force acting uponcompression spring 32 is transferred directly to the extension spring34, and the compression spring thereafter is inelfective to yieldablyoppose movement of the contact assembly. The springs are so adjustedthat the transfer preferably is arranged to occur at a depth. other h nhe ep t which h Contact lsmsn en ages he. step member for the reasonthat contacting thereof at the proper depth is difiicult when thecontacting occurs during the transfer period. The adjusting member 36 isdisposed about the member 35 and is adapted to engage the springcentering washer 33 in an abutting relation therewith to preload thecompression spring, the spring rate of the extension spring being variedby the adjusting member 37 which varies the number of active turnstherein. The purpose of the aforesaid adjusting members will appear ingreater detail hereinafter.

The casting 26 is provided with a recessed flanged portion 38 withinwhich is mounted a cover 39 securely clamped by a ring member 41 whichis crimped to the flanged portion of the casting, the cover 39 andmember 41 each being composed of a material upon which ice coatings willnot form such, for example, as Lucite. The cover 39 is provided with alower reduced end portion about which a slip ring 42 composed of anysuitable electrical conducting material is arranged, electricalconnection to the slip ring being provided by a contact element 43engaging the slip ring and extending exte-riorly of the ring 41, asuitable insulating ring 40 being disposed intermediate the cover 39 andflanged portion 38 of casting 26.

Arranged about the inner circumference of the cover 39 is a step member44 composed of a suitable conducting material and conveniently formedinto the shape illustrated in any convenient manner, preferably bypunching the member from a thin strip or sheet of material. The stepmember is soldered to the slip ring by means of cars 45 formedintegrally with the step member, the member 44 being insulated frombellows 24 by an insulating sleeve 50. Fig. 7 is a detailed view of thestep member 44 which is provided with a plurality of indentations orsteps adapted to be engaged by the contact element 16 selectively inaccordance with a predetermined depth selection as will appear moreclearly as the description proceeds.

The instant device is adapted for use with a depth charge pistol of thetype shown in Figs. 1 through 3, which pistol is described and claimedin the copending application of R. M. Cate et al. for Depth ChargeArming Device, Serial No. 596,065, filed May 26, 1945. The aforesaidpistol will now briefly be described and reference is made to theaforesaid application for a more detailed description thereof.

An electroresponsive detonator assembly 46 is arranged in predeterminedspaced relation with respect to a booster charge 47, the detonatorassembly being adapted to be rotated into operative relation with thebooster charge by a dual bellows arrangement under pressure of thesurrounding water. The aforesaid bellows arrangement comprises the fluidfilled bellows 43 and 49 separated by a partition 51 having an orifice52 therein such that flow of fluid from bellows 48 to bellows 49 isrestricted, thus preventing substantial movement of the bellows 48 and49 when external shocks such, for example, as countermine shocks or theblow received in striking the water is received by the bellows. Flow offluid between the bellows, however, in response to pressure graduallyapplied to bellows 48 by the surrounding water as the associated depthcharge descends through the water is sufficient to cause displacement ofthe bellows.

The bellows 48 and 49 are secured to the partition 51 and a plunger 53is secured to the free ends of the bellows and is adapted to passthrough the partition slideably. The plunger 53 is connected at itsinner end to a linkage generally indicated by the numeral 54 which inturn is operatively secured to the detonator assembly 46 such that thedetonator assembly is rotated into operative relation with the boostercharge 47 when a sufiicient displacement of the dual bellows arrangementis produced. A plurality of spring members 55 are employed to controlthe depth at which the rotation of the detonator assembly is completed.

A plurality of electrical switches are also employed in the pistol andare adapted to be operated in predetermined sequential order to completecertain electrical circuits comprising the firing control system of adepth charge, one of such switches comprising contacts 56 and 57 andcontacts 58 and 59, Fig. 9, adapted to close the detonator circuit whenthe detonator assembly is rotated into operative relation with thebooster charge. The remaining switches comprising contacts 61 and 62 andcontacts 63 and 64 respectively, Fig. 9, are hydrostatically operatedand are utilized to apply static operating potentials from a source ofpower to the electron discharge devices included in the firing controlsystem described in the aforesaid application.

The hydrostatically controlled switch of the instant invention issupported on the cup-shaped member 65 of the aforedescribed armingdevice and secured thereto by a nut 66 disposed about the externallythreaded portionof the casting 26, suitable gasket means 67 beingarranged between the flanged portion of the casting and the cupshapedmember 65 to insure a water-tight connection therebetwcen. it will benoted that an orientating pin 68 is secured to the flanged portion ofthe casting, a hole being cut in the cup-shaped member 65 for receivingthe orientating pin.

An indexing device generally indicated by the numeral 69 is provided forthe switch and comprises a substantially cylindrical shaft 71 having aflat surface extending the length thereof, the cover 39 having a holecut therein for receiving the shaft 71. The cover 39 and shaft 71 areadapted to be rotated by turning a knob 72, which knob has an arm 73extending radially therefrom. A disc 74 and bearing member 75 rotatewith the shaft and knob,

the disc 74 having affixed thereon suitable indicia, Fig. l, forindicating a plurality of depths of submergence correspondingrespectively to the plurality of indentations formed on the step member44, the bearing member 75 being disposed within a hole in the cover 76of the pistol. A spring member 77 is aflixed to the bearing member 75 asby swaging and is provided with oppositely disposed ears 78 adapted toengage a plurality of indentations 79 circumferentially arranged inpredetermined spaced relation on the inner surface of the pistol cover76, the spring member also being adapted to p-reload a gasket 81disposed intermediate the disc '74 and cover 76.

A conductor is soldered to the lower extremity of rod 13 to establish anelectrical connection to the detonator 46 while another conductor 82 issoldered to the contact element 43 to establish electrical connectionbetween the switch and a sea cell 83, the sea cell being supported on abracket 84 secured to the post member 85 by a nut 86. The sea cell 83may be of any suitable type adapted to generate an electric potentialwhen immersed in sea water. A conductor 87 extends from the positiveterminal of the cell 83 to a terminal 88 aflixed to a horizontal stripof insulating material 89, the strip 89, in turn, being supported on thepost member 91 by a nut 92. A second terminal 93 is aflixed to the strip89 and is adapted to receive conductor 82, a suitable strip ofconducting material 94 being connected between the terminals to maintainelectrical connection there'between.

The operation of the switch of the present invention will now bedescribed with reference to Fig. 4 of the drawings. The cylindricalmember 10 and contact element 16 carried thereby and the tubular member11 comprise a piston adapted to be moved inwardly under pressure of thesurrounding water, the compression spring 32 and extension spring 34acting in parallel and serving to yieldably oppose such inward movement,thereby to control the displace ment of the members 10 and 11 inaccordance with the value of water pressure acting thereon. As the waterpressure increases, the tubular member 11 causes the washer 31 to moveinto engagement with the adjusting member 35 whereupon the compressionspring '32 is rendered ineffective to further oppose the inward movementof members 10 and 11 and the force acting thereon is transferred to theextension spring 34 which further controls the displacement of members10 and 11 in accordance with the value of water pressure. It will beunderstood, at this point, that for 'agiven depth of sub-' weapon in iion the ctu l pres ur exer ed. on he suI SS 3 and 34 is less than thetheor tical p essure e ed e eon since the eifec tive area of bellows 24decreases progressively as the switch descends through the Water, suchcondition becoming more clearly manifest at greater depths ofsubmergence. In order to maintain the linearity desired in depthselecting for firing at greater depths, the indentations on the member44 are formed non-linearly, the spring rates of each of the springsbeing linear.

The adjusting members 36 and 37 are provided in order that the opposingforce exerted by the springs 32 and 34 respectively may be varied tocalibrate the displacement of the contact element 16 in accordance withthe water pressure at a predetermined depth. The contact element 16 isadapted to engage one of the plurality of indentations of the stepmember 44 selectively in accordance with the depth preselected by theindexing device 69, such preselection being accomplished by rotating theknob 72 until the numeral on the disc 74 indicating the desired depthalines with the arrow 95 formed on the cover 76, thus placing thecorresponding indentation on the member 44 directly beneath the contactelement 16.

Let it be assumed, by way of example, that the hydrostatic switch of thepresent invention is employed in an arming device of the type describedin the aforesaid application of R. M. Cate et al. and that the armingdevice is utilized in a depth charge having a firing circuit similar tothat described and claimed in the co-pending application of Harry H.Hall et al. for Means for Firing an Explosive Charge, Serial No.520,074, filed January 23, 1944, which firing circuit is shownschematically in Fig. 9 and comprises a signal pickup device which controls the operation of a suitable amplifier. The amplifier, in turn,controls the operation of a firing relay 96 which, when operated,completes an electrical circuit from a battery 9'7 to the detonator 46,thereby exploding the depth charge. In such case, the hydrostaticallycontrolled firing system provided by the switch and sea cell 83supplements the influence firing system controlled by the proximity of asubmarine in order to insure the detonation of the depth charge in theevent that the depth charge does not pass sufficiently close to thetarget submarine to actuate the influence firing system. Such anarrangement is especially desirable when a convoy of ships is underattack by enemy submarines since the positive detonation of depthcharges will, at least, drive the attacking submarines from thevicinity.

Let it be assumed, for the purpose of description, that a depth chargeemploying both the influence and hydrostatic firing systems is launchedfrom a surface vessel and directed at a submarine. Let it further beassumed that before the launching, the hydrostatic system is adjusted totire at a depth of 300 feet by rotating knob 72 until the number 300 ondisc 74 alines with arrow 95, thereby placing the indentation marked 300on the step member .44, Fig. 7, directly beneath the contact element 15.

As the depth charge descends through the water, hydro static pressurecauses contacts 61 and 62 to close as well as contacts 63 and 64-,thereby applying static operating potentials to the electron dischargedevices included in the influence firing system. The hydrostaticpressure also causes a lead diaphragm 100, formed integrally with thecontainer for the sea cell, to be ruptured when the pressure reaches apredetermined value, thereby admitting the sea Water to the cell toactivate the same. Thus, by reason of this arrangement a safety featureis provided in that no potential is applied to the detonator before thedepth charge is immersed in water although the detonator is otherwisefully armed as by inadvertenceor accident. As the depth charge continuesto descend through the water, the detonator 46 is rotated into operativerelation with the booster charge 47 by the bellows 48 and 49 underpressure of the surrounding water.

the detqnat r m es nt the armed. t sls timt,v c9 1.- tact 56 moves intoengagement with contact 57 and contact 58 moves into engagement withcontact 59 whereby the depth charge is electrically armed.

If the path of descent of the depth charge is suff ciently close to thesubmarine and if the depth charge moves within the influence zone of thesubmarine before a depth of 300 feet is reached, the influence systemoperates to close relay 96 and complete a circuit from battery 97 to thedetonator 46 to explode the charge. in the event, however, that the pathof descent of the depth charge is not sufiiciently close to thesubmarine to actuate the influence firing system, the hydrostaticallycontrolled system will be caused to operate in the fol lowing manner. Asthe depth charge descends through the water, water seeps into theinterior of the switch through a hole 98 in the cover and through thminute space between the cover and ring member, the resulting waterpressure reacting upon the piston assembly comprising contact 16,cylindrical member 10 and the tubular member 11 to cause inward movementthereof against the compression spring 32.

The aforesaid assembly continues to move inwardly as the depth chargesinks deeper and the water pressure increases, with the spring 32providing substantially all of the torce opposing such motion until adepth of 200 feet is reached. When this occurs, the washer 31 engagesthe adjusting member 35 and spring 32 is cut out, whereupon, theextension spring 34 alone exerts the force. tending to oppose the inwardmotion of the assembly. When the depth charge sinks to a depth of 300feet, the contact element 16 will have traveled the distance necessaryto engage the 300 ft. step on member 44 to complete a circuit from thesea cell 83, through the contact 43, slip ring 42, step member 44,contact 16, rod 13, conductor 80 and detonator 46, thus exploding thedepth charge.

Under certain submarine attacking conditions, it may be desirable tocause the depth charge to become active only by the proximity of thesubmarine, in which case the hydrostatically controlled firing systemmust be rendered ineffective before the launching of the depth charge.Accordingly, the step member 44, when assembled within the ring member39, does not form a closed cylinder but provides a slot 9 through whichcontact 16 passes when the knob 72 is adjusted to aline the letters INformed on disc 74! with the arrow 95. With the step member so adjusted,contact 16 engages the cover 39 as the contact is moved inwardly underpressure of the surrounding water thereby preventing the completion ofa. circuit from the sea cell 83 to the .detonator 46.

Whereas, in the foregoing it was assumed that the switch of the instantinvention is to be utilized in connection with influence firing systemsfor depth charges to provide selective firing thereof, it will, ofcourse, vbe understood that the switch may be used singularly in a depthcharge to provide a hydrostatically controlled firing system, in whichcase the firing system comprises the switch of the present invention,sea cell 83 and the detonator assembly 46.

In the event that a sudden increase in pressure of the surrounding wateris produced during the descent of the depth charge by the detonation ofa neighboring charge,

for example, the fiow of water into the switch through hole 93 and theminute space between the cover 39 and ring member 41 is restricted ordamped whereby the piston is prevented from moving inwardly in responseto such sudden increases in water pressure.

Moreover, it will be noted that the contact element 16 is adapted toengage the interior of casting 26 if the depth charge descends beyond1500 feet without being fired. When this occurs, the detonator becomesshortcircui ted and the ,depth charge is sterilized.

From the foregoing it should now be apparent that ,a hydrostaticallycontrolled switch has been provided which is well adapted to fulfill theaforesaid objects of the invention.

While the invention has been described in particularity with referenceto an example thereof which gives satisfactory results, it readily willbe apparent to those skilled in the art to which the inventionappertains, after understanding the invention, that further embodiments,modifications and changes may be made therein without departing from thespirit and scope thereof as defined by the claims appended hereto.

The present invention may be manufactured and used by or for theGovernment of the United States of America for governmental purposeswithout payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A pressure responsive device of the character disclosed comprising,in combination, a piston movable under hydrostatic pressure, a contactelement carried by said piston, settable contact means including aplurality of steps arranged in spaced relation with respect to saidcontact element and adapted to be engaged thereby selectively inaccordance with the setting of the contact means when hydrostaticpressure suflicient to move said piston is applied thereto, means foryieldably opposing the movement of said piston thereby to cause saidelement to engage said steps selectively at preselected depths of submergence respectively corresponding thereto, and means including saidcontact means for preselecting and setting one of said steps thereof formutual engagement with said element.

2. A pressure responsive device of the character disclosed comprising,in combination, a piston movable under hydrostatic pressure, a contactelement carried by said piston, settable contact means including aplurality of steps arranged in spaced relation with respect to saidcontact element and adapted to be engaged thereby selectively inaccordance with the setting of the contact means when hydrostaticpressure sufiicient to move said piston is applied thereto, means foryieldably opposing the movement of said piston thereby to cause saidelement to engage said steps at substantially preselected depths ofsubmergence respectively corresponding thereto, adjusting means forvarying the operation of said opposing means thereby to cause saidelements and steps to mutually engage at depths which closely correspondto said preselected depths, and means including said contact means forpreselecting any one of said steps for mutual engagement with saidelement.

3. A switch adapted to be immersed in a body of water and comprising, incombination, a member adapted to be moved along an axis when hydrostaticpressure is applied thereto, a contact element carried by said memberand arranged transversely of said axis, means f r controlling thedistance traveled by said member in accordance with the depth ofsubmersion of said switch, contact means rotatable about said axis andhaving a plurality of steps circumferentially disposed about the axiscorresponding respectively to a plurality of depths of submersion, andmeans for rotating said contact means to aline one of said plurality ofsteps with'said contact element thereby to preselect one of saidplurality of depths of submersion at which said contacts will mutuallyengage.

4. A switch adapted to be immersed in a body of water and comprising, incombination, a piston movable under hydrostatic pressure, a contactelement carried by said piston, settable contact means having aplurality of steps arranged in spaced relation with respect to saidcontact element and adapted to be engaged thereby selectively inaccordance with the setting of the contact means as said switch descendsthrough the water, means including said contact means for preselectingone of said steps for mutual engagement withsaid element, means foryieldably opposing the-movement of said piston thereby to cause saidelement and steps to mutually engage at a plurality of depths ofsubmergence respectively corre sponding thereto, said opposing meanscomprising a firstv resilient means for opposing the movement of said"plunger over a predetermined range of depths and a second resilientmeans for opposing the movement of the plunger over a difierentpredetermined range of depths, and means for coupling said first andsecond resilient means in such a manner to render the first resilientmeans ineffective over said diiferent predetermined range of depths.

5. In a firing circuit for a depth charge adapted to be armed as thedepth charge descends through a body of water, the combination ofhydrostatic means for arming said. circuit, an electroresponsivedetonator included in said circuit, means connected in the firingcircuit and effective when immersed in salt water for generatingelectrical energy for firing said detonator when the circuit iscompleted, a water-tight housing for said generating means, said housinghaving a diaphram formed integrally therewith and adapted to be rupturedby the pressure of the surrounding water thereby to admit water to thegenerating means, and hydrostatically controlled means for completingsaid firing circuit after the circuit has been armed.

6. A pressure responsive device of the character disclosed comprising,in combination, a piston movable under hydrostatic pressure, a contactelement carried by said piston, a settable contact means including aplurality of steps arranged in spaced relation with. respect to saidcontact element and adapted to be engaged thereby selectively inaccordance with the setting of the contact means when hydrostaticpressure sufiicient to move said piston is applied thereto, means forelfectively reducing electrical leakage between said contact element andsaid contact means caused by electrolytic action therebetween, means foryieldably Opposing the movement of said piston thereby to cause saidelement and steps to mutually engage at preselected depths ofsubmergence respectively corresponding thereto, and means including saidcontact means for preselecting and setting one of said steps for mutualengagement with said element.

7. in a firing mechanism for a depth charge, a piston in communicationwith the surrounding water and arranged to be moved along its axis inresponse to hydrostatic pressure thereon, means for yieldably opposingmovement of the piston whereby the piston is moved variably inaccordance with the water pressure thereon, a contact element carried bysaid piston for movement therewith, an electroresponsive detonatorconnected to said contact element, a settable stepped conductor spirallydisposed about said piston and rotatable about the axis thereof into anyone of a plurality of difierent initially spaced positions with respectto said contact element for engagement therewith at any one of aplurality of depths of submergence corresponding respectively to saidplurality of difierent positions, and a source of energy connected tosaid stepped conductor and to said detonator whereby the detonator isfired by energy received therefrom as the contact element engages saidconductor.

8. A pressure responsive device comprising in combination, means movablein response to hydrostatic pressure, a contact element carried by saidmovable means, an annular contact settable at will to differentsettings, a plurality of steps on said annular contact for engagementwith said contact element as the movable means is moved from an initialposition to a selected position, and means for moving said annularcontact to a selected setting.

9. A switch for a depth charge adapted to be immersed in a body of watercomprising, in combination, means movable in response to a predeterminedhydrostatic pressure, a contact element carried by said pressureresponsive means, an annular contact rotatably supported on said switchand having a plurality of steps corresponding to a plurality of depthsof submersion, and actuating means secured to said annular contact forselecting one of said 1,789,158 plurality ofdepths of submersion atwhich said corltacts 1,844,575 will engage. 2,110,552

References Cited in the file of this patent UNITED STATES PATENTS 5316,382

1,314,413 Martena Aug. 26, 1919 263,985 1,314,662 Huber Sept. 2, 1919532,841 1,368,569 Minklcr Feb. 15, 1921 297,182

10 Rudolph et a1. Jan. 13, 1931 Harrison Feb. 9, 1932 Hayden Mar. 8,1938 FOREIGN PATENTS Germany Nov. 26, 1919 Italy Apr. 10, 1929 GermanySept. 11, 1931 Italy June 6, 1932

